In the field of semiconductor fabrication, a variety of process steps results in the contamination of the apparatus or equipment used to perform a particular processing step. FIG. 1 depicts a conventional wafer processing apparatus 100 illustrative of a high density plasma (HDP) reactor including a semiconductor plate 109 and quartz sidewalls 112 that define a chamber 106. Apparatus 100 includes an electrostatic chuck (ESC) 102 that is suitable for receiving a semiconductor wafer 104 within chamber 106 and a set of coils 108 configured to produce an electromagnetic field within chamber 106.
Introducing appropriate gases into chamber 106 when the coils 108 are producing an electromagnetic field while maintaining chamber 106 at an appropriate pressure will result in the formation of a plasma as is well known in the field. In one embodiment, the plasma generated in chamber 106 is used to etch material from wafer 104, which typically includes numerous layers of differing materials. During the plasma etch of one of the materials, it is possible to expose portions of an underlying material.
When portions of an underlying material are exposed, the plasma in chamber 106 may generate atomic particles comprised of the underlying materials. During a plasma etch of an interlevel dielectric, for example, it is possible to release metallic particles (or other contaminants) from an underlying interconnect layer into chamber 106. The presence of these metallic particles in chamber 106 during a plasma etch may result in an undesired diffusion or high energy physical implant process in which the metallic particles are incorporated into the surfaces, such as plate 109, of apparatus 100 that are exposed to chamber 106. In fabrication processes utilizing copper interconnects, for instance, a post-copper oxide etch process, such as a via etch, may introduce copper atoms into plate 109 and sidewalls 108.
FIG. 2 depicts an alternative embodiment of apparatus 100 illustrating an inductively coupled, parallel plate etch system. This embodiment of apparatus 100 includes a set of coils 120 that are configured to form an electro-magnetic field in a chamber 116 that is substantially enclosed by silicon dome 110. As depicted in FIG. 2, system 100 may further include quartz lights or heat lamps 122. Apparatus 100 of FIG. 2 is suitable for a variety of processes including the dielectric etch process described with respect to apparatus 100 of FIG. 1. Similar to apparatus 100 of FIG. 1, a semiconductor process, such as a plasma oxide etch, performed in apparatus 100 of FIG. 2 may result in the unwanted contamination of silicon dome 110 that can affect the generated plasma and result in an etch stop condition.
In some of the more common materials (e.g., silicon) typically utilized for plate 109 of FIG. 1 and dome 110 of FIG. 2 (collectively referred to herein as enclosures), copper atoms are believed to be highly mobile. As these mobile and conductive particles are introduced into an enclosure, the electrical characteristics of the enclosure may be affected thereby altering the characteristics of the electromagnetic field produced by coils 108 and 120 in chambers 106 and 116 respectively. The alteration of the electromagnetic field by the presence of mobile contaminants in an enclosure may negatively affect the plasma characteristics and possibly result in a less efficient etch process. If the plasma is sufficiently affected by the presence of conductive particles in the enclosure, an etch stop condition may result in which the process is entirely unable to etch vias into an oxide layer of wafer 104.
In addition, typical etch processes such as the plasma etch of silicon-oxide films utilizing a carbon fluorine chemistry tend to result in the formation of a polymer layer on the exposed surfaces of an enclosure. If the thickness of the polymer layer formed on the enclosure is sufficient, the dome may be unable to contribute silicon or other atoms that participate in the chemistry of the plasma etch process thereby further decreasing the efficiency of the process.
In the apparatus 100 of both FIG. 1 and FIG. 2, a contaminated plate 109 or dome 110 resulting from extended processing typically requires periodic replacement or refurbishing. Typically, the replacement of plate 109 or dome 110 is undesirably costly. In addition, conventional methods of refurbishing enclosures typically require bead blasting or other similarly crude cleaning processes necessitating the removal of the enclosure from apparatus 100. After an enclosure is refurbished, it must be reinstalled on apparatus 100 and re-qualified. Skilled artisans appreciate that the removal and requalification of an enclosure can be a costly and time-consuming process. Therefore, it would be highly desirable to implement an apparatus and method that would minimize or eliminate overhead associated with replacing or refurbishing an enclosure such as plate 109 or dome 110.